Scientists stunned to find Marijuana has this huge negative effect on the brain

A new study finds that heavy pot smokers are taking a big risk.

Marijuana is often depicted as an entirely safe form of drug that is even medically beneficial — but a new study indicates that there is one big side effect on the brain.

New research claims that long-term use of marijuana could cause problems down the road with verbal memory, according to a Reuters report.

The study, which followed thousands of young people into middle age, found that those who used marijuana tended to perform more poorly on verbal memory tests, although other brain functions appeared unaffected by the drugs. Scientists were surprised to find such a consistent link between verbal memory and chronic marijuana use, said lead author Dr. Reto Auer of the Univerity of Lausanne in Switzerland, according to the report.

The findings are based on 25 years of data from about 3,500 young adults who completed standardized tests. The individuals were between 18 and 30 years of age when the study began in the 1980s. About 80 percent of them self-reported smoking marijuana, although just 12 percent were still smoking in middle age.

The study also found that verbal memory scores decreased the more that marijuana was used. For every five additional years of exposure, about half of marijuana users would remember one less word from the 15-word verbal memory test.